1. Field of the Invention
This invention is in the field of manufacturing apparatus and, more particularly, relates to a transfer system for removing fixtures holding a workpiece from the bottom of a stack of such fixtures stored in a transferor magazine and for loading such fixtures and stacking them serially in a transferee magazine. The magazines are removably mounted on their respective bases, and a transport mechanism transports the fixtures from a transferor station in the transferor base to a transferee station in the transferee base where a fixture loader loads fixtures into the transferee magazine a fixture at a time.
2. Description of the Prior Art
The development of integrated circuit (IC) chips, particularly medium and large scale IC chips, has created a need for improved manufacturing processes which lend themselves to automating the connecting of the conductive leads of a lead frame on which an IC chip is bonded to substrates when the IC chips are interconnected to form useful electronic circuits. In implementing such processes, fixtures such as those described and illustrated in U.S. Pat. No. 4,069,496, which issued on Jan. 17, 1978, can be used to removably hold a segment of a film strip on which an IC chip has been bonded to a lead frame, which frame is, in turn, attached to the segment.
In automating the processes of manufacturing hybrid substrates, a plurality of fixtures is assembled, or collected, in a magazine such as that described and illustrated in application Ser. No. 06/153,367 filed May 27, 1980, entitled "Material Handling Apparatus," which application is assigned to the same assignee as this application. Each of the fixtures stored in a magazine such as that disclosed in application Ser. No. 06/153,367 filed May 27, 1980, now U.S. Pat. No. 4,346,817 may have as its workpiece an IC chip bonded to a segment of film held by each fixture. Each such magazine has the capability of having such fixtures inserted into the magazine and subsequently removed as steps in the process of manufacturing electronic circuits.
U.S. Pat. No. 4,068,767, which issued on Jan. 17, 1978, is the closest relevant prior art known to applicant. This patent teaches a transfer mechanism which withdraws a fixture from the bottom of a stack of such fixtures in a transferor magazine and inserts them serially into the bottom of a stack of such fixtures in a second, or transferee, magazine. The transfer mechanism includes a linear actuator which, in cooperation with cam surfaces, loads or inserts fixtures, a fixture at a time, into the transferee magazine.
The transfer system of this invention is designed to use a magazine such as that disclosed in FIGS. 12 through 15 of application Ser. No. 06/153,367, filed May 27, 1980, now U.S. Pat. No. 4,346,817 the disclosure of which is incorporated by reference herein, in performing various manufacturing steps on the workpiece, i.e., the IC chip, mounted on each fixture; such as, testing the chip; providing machine readable identification of the workpiece on the segment of the film strip on which the workpiece is mounted; reading the data so encoded, blanking a chip and its leads from the segment, forming its leads, and mounting a chip and its formed leads on a substrate; removing the segment from which an IC chip has been excised from a fixture, and mounting a segment with a chip mounted thereon on a fixture to repeat the process.
Problems with prior art systems are that they require a linear actuator that limits the flexibility of the transport system with respect to transporting fixtures from the transferor magazine to one or more work stations and ultimately to a transferee magazine and storage therein. Another problem with prior art transfer systems is that the means for loading fixtures into the transferee magazine applies forces to the fixtures and their workpieces which can damage the workpiece mounted on a fixture. Another problem with prior art systems is that they do not permit precise control of intermittent movement of a plurality of fixtures unless the fixtures are in contact with each other.